Geologists have long known that the Earth's mantle is heterogeneous, but its spatial arrangement remains unresolved—is the mantle essentially layered or irregu larly heterogeneous?

地质学家早就知道地球的地幔是不均匀的，但是它的空间排列仍然没有确定——地幔本质上是分层的还是完全不均匀的？